1. Field of the Invention
This invention relates to an optical switch array suitable for effecting the connection of the signal lines of communication network, computers or the like through the medium of a light.
2. Related Background Art
A switch array is an indispensable device in the fields of communications and computers and in particular, a cross bar switch is very useful because of its characteristics.
However, the cross bar switch array is difficult to manufacture if the connection terminals thereof are increased, and it is not easy to make a large-scale switch array even if the present-day semiconductor technique is freely used.
Therefore, the cross bar switch is often used in connecting a small number of terminals.
On the other hand, recently, the optical art tried to make relatively large-scale cross bar switches, and the details thereof are disclosed, for example, in IEEE SPECTRUM, August 1986 and IEEE COMPUTER, June 1987. (P. 50), A. A. Sawchuck et al.
FIG. 1 of the accompanying drawings is a schematic view showing such an optical cross bar switch according to the prior art. In FIG. 1, the reference numerals 9-1, 9-2, 9-3 and 9-4 designate light sources, the reference numeral 92 denotes emitted light beams from the light sources 9-1, etc., the reference numeral 93 designates a shutter array, the reference numeral 94 denotes light beams transmitted through the shutter array 93, and the reference numerals 95-1, 95-2, 95-3 and 95-4 designate photodetectors.
The present example shows an optical cross bar switch in which the number of shutters is 4.times.4. Signals from respective terminals are supplied to the light sources 9-1, 9-2, 9-3 and 9-4. The emitted light beams 92 from the light sources 9-1, 9-2, 9-3 and 9-4 are widened in a vertical direction and enter the shutter array 93.
In FIG. 1, those portions of the shutter array 93 which are indicated by hatching are light transmitting portions, and the transmitted light beams 94 from these transmitting portions are collected in a horizontal direction and enter the photodetectors 95-1, 95-2, 95-3 and 95-4. Signals from the photodetectors 95-1, 95-2, 95-3 and 95-4 are supplied to respective terminals.
Which terminal should be connected together at this time is determined by which shutter of the shutter array 93 is rendered transmissive.
A description will now be provided of the connection of the light source 9-1 as an example. The signal of the terminal connected to the light source 9-1 is modulated by the light beam emitted from the light source 9-1, and is widened in a vertical direction and enters the first row of the shutter array 93. When as shown in FIG. 1, for example, the shutter in the third column and the first row is a transmitting portion, the incident light beam passes through only this shutter, is collected in a horizontal direction and is detected by the photodetector 95-3.
Thus, the terminal of the light source 9-1 is connected to the terminal of the photodetector 95-3. This also holds true of the connection between other terminals.
However, in the above-described example of the prior art, an increase in the number of terminals connected together results in an increase in the number of the shutters of the shutter array 93 and it becomes difficult to make the optical cross bar switch. Where computers are connected, the connection signal lines of a computer may amount to several tens to about one hundred.
For example, where ten computers each having one hundred connection signal lines are to be connected, a shutter array having 100.times.10=1000 light sources and photodetectors and 1000.times.1000=10.sup.6 shutters becomes necessary, and it becomes very difficult to make a shutter array having such a huge number of shutters.